Apparatus and method for continuous casting of metals



United States Patent [72] Inventor Alfred J. Wertli l5 Poststrasse, CH 8406 Winterthur, u Switzerland [21] Appl. No. 822,767 [2 2l I- iled Jan. 29, 1969 4 Division ofSer. No. 618,415, Feb. 24, 1967, l 7

now Pat. No. 3,502,135 7 W [45] Patented Sept. 29, 1970 ma [32] Priority March 31, 1966 [3 3 Switzerland 31 1 5,060/66 [54] APPARATUS AND METHOD FOR CONTINUOUS CASTING 0F METALS 2 Claims, 3 Drawing Figs.

[52] 11.8. ("I 164/82 [51] Int. Cl B22d 11/00 [50] Field of Search 164/61, 62,

References Cited UNITED STATES PATENTS 2,173,990 9/1939 Wood et al. l64/253X' 2,915,797 12/1959 Hoehl 164/61 3,307,231 3/1967 Andrews 164/144 Primary Examiner-.l. Spencer Overholser Assistant Examiner-R. Spencer Annear I A ttorney- Kenyon and Kenyon, Reilly, Carr and Chapin ABSTRACT: An apparatus for maintaining intimate contact between a mold and cooling device in a continuous casting operation. The contact surface between the mold and cooling device is subjected to a reduced pressure by a vacuum transmitted through apertures in the cooling device which communicate with the contact surface. The mold can also be sealed to the atmosphere and supplied with nitrogen to prevent oxidation where graphite molds are used.

Patented Sept. 29, 1970 3,530,926

Fig. 1 7

. Inventor:

ALFRED J. Wsnfu This is a division of copending application Ser. No. 618,415, filed Feb. 24,, 1967, now US. Pat. No. 3,502,135.

The invention relates to an apparatus and method for continuous casting of metals. More particularly, the invention relates to an apparatus and method having at least one mold cooled by a surrounding cooling device.

Heretofore structures and methdds have been know n and used wherein a metal casting has been formed by a mold which has been surrounded by a cooling device. However, difficulties have risen repeatedly since it has not been possible to obtain and maintain a permanent intimate contact between the mold and cooling device. The difiiculties have originated from the different temperatures to which the mold and cooling device have been subjected, for example, the molten metal within the mold can subject the mold to a temperature above 1,000C while the cooling device is subjected to prevailing temperatures between 60and 100C. Because of the differences in these temperatures and also because of the nonuniformity in heatsdistribution in the contacting surfaces between the mold and cooling device, stresses have arisen in the mold or in the cooling device which have subsequently lead to deformation of these parts. Such deformations result in the formation of air gaps or spaces between the mold and cooling device in the plane of the contacting surfaces. This has impaired the heat transfer from the mold to the cooling device and has consequently led to interruptions in the continuous casting process so that at least the quality of the cast strand is considerably lowered.

It is an object of the invention to provide for a uniform heat transfer from a mold to a surrounding cooling device during a continuous casting process.

it is another object of the invention to maintain a con tinuous contact surface between a mold and a surrounding cooling device during a continuous casting process.

Briefly, the invention provides a method of maintaining the contacting surfaces of a mold and a cooling device surrounding the mold in intimate contact with each other during a casting operation. Intimate contact is maintained by producing a reduced-pressure between the surfaces of the mold and cooling device which has the effect of drawing the mold onto the cooling device. The adjacent surfaces of the mold and cooling device thus are always in complete contact so as to avoid the formation of air gaps therebetween while insuring a good uniform heat transfer during each phase of the casting operation. The method of the invention is particularly advantageous in the continuous casting of strips since the molds for such have a large width and thus a large heat transfer surface.

The apparatus of the invention includes a cooling device for surrounding a mold of a continuous casting device wherein the contacting surfaces of the mold and cooling devices communicate through a plurality of apertures within the cooling device with a means for generating a reduced-pressure.

, These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a cross section view of a mold and cooling device of the invention;

FIG. 2 illustrates a view taken iir lirre A B of FIG. 1i and FIG. 3 illustrates a cross-sectional longitudinal view of a modification of the invention.

Referring to FIG. 1, a cooling device having an upper part 1 and .a lower part 2 held together, for example, by bolts (indicated by broken lines 3) is secured around a mold 4. The

mold 4 is likewise divided into upper and lower parts to define a hollow internal longitudinal space 5 which serves to form a strip shaped cast strand. The upper and lower parts 1, 2 are I each provided with chambers 6 through which cooling medium, such as water, oil or the like, flows in a manner not shown in detail.

Referring to FIGS. 1 and 2, a plurality of apertures 7 are formed in the upper and lower parts 1, 2 of the cooling device between the mold 4 and the chambers 6 in each'respective part 1, 2. The apertures 7 are uniformly distributed over the cooling device and communicate at one end with the contact surfaces 8,9 between the mold 4 and the respective parts 1, 2 of the cooling device. The opposite ends of the apertures 7 communicate with a series of passages l0, 11 in each respective part 1, 2 of the cooling device. The passages l0, 11 which are disposed, for example, transversely of the longitudinal axis of the mold 4 are interconnected by a respective transverse During a casting operation, the reduced-pressure generating means creates a reduced pressure, for example, of 7 p.s.i., across the contacting surfaces 8, 9 between the mold 4 and each of the parts 1, 2 of the cooling device. The effect of such a reduced-pressure is that the mold 4 is maintained flush with the parts 1, 2 of the cooling device along the contact surfaces 8, 9 so that a good uniform heat transfer from the mold to the cooling device is constantly provided. The formation of air gaps in the contact surfaces 8, 9 is prevented even if the walls of the cooling device in which the apertures 7 are formed are slightly deformed, as by bending since the adjacent mold walls will also be subjected to similar deformation.

Each part 1, 2 of the cooling device is provided with apertures 7 which are cylindrically formed along their lengths on the left of each part, as shown in FIG. 1, and apertures 7 which are conically widened at theier ends adjacent the contact surfaces 8, 9 on the right of each part, as shown in FIG. 1. 'The conically widened apertures provide an increase in the suction area between the contact surfaces 8, 9 so that a greater suction force per aperture is created to press the mold 4 against the cooling device. It is noted in this regard that the reduced pressure is substantially uniform in each of the apertures of the cooling device. It is further noted that since the heat transfer from the mold to the cooling medium (e.g. water) is conducted through the cross section of the metal of the cooling device, by maintaining the diameter of apertures 7 as small as possible within the parts 1, 2 and by widening the ends of these apertures, a good suction area is obtained without a cermet(sintered compound of metallic and ceramic substance). Where the mold material is graphite, the invention can be advantageously improved by feeding nitrogen to the exit of a cast strand from the mold 4.

Referring to FIG. 3, a mold of graphite which is connected to a furnace 26 is surrounded by a cooling device as described above having upper and lower parts 1, 2 with cylindrically formed apertures 7 and by a housing 20 mounted on the exit end of the mold. The housing 20 is connected to a supply of nitrogen 21 (schematically shown) and surrounds .a solidified strand 22 emerging from the mold. A labyrinth seal or gland 23 is provided between an inwardly directed wall of the hous-- ing 20 and the casting 22. Nitrogen is supplied to a pair of passages 24 in the housing 20 which distribute the nitrogen through a plurality of ports 25 into the interior of the housing 20 over the width of the strand 22. The nitrogen is fed under a slight excess pressure to so that oxidation of the the mold and is drawn off by a reduced-pressure generating means acting on the mold as described above.

The molten metal or metal alloy in the furnace which is to be cast, enters the mold 4 at the end connected to the furnace,

solidifies undertheacTionof the cooling device, and is continuously or discontinuously drawn out by means (not shown) from the mold in the direction indicated by the arrow 27.

It is noted that the apertures 7 need not be formed in the walls of the cooling device. Instead, individual plates which are to be considered as components of a cooling device can be provided between a mold and the remainder of the cooling device. These plates are formed of heat conducting material and are provided with apertures 7 together with transverse connecting passages l0, 11 as described above. If desired, the apertures 7 can extend through the entire depth of thicknesses of the plates so that a reduced-pressure will then act both on the contact surface between plate and mold as well as on the contact surface between plate and the remainder of the cooling device.

The invention provides for the simplified construction of a mold. For example, when casting broad strips, it is no longer necessaryto manufacture the mold over the entire width from a simple piece. Rather, the mold of the invention can be assembled from several narrower pieces which together extend over the entire width of the strand to be produced since the mold portions lying side by side are safely and permanently held against a cooling device under the reduced-pressure created by the reduced-pressure generating means of the invention. Likewise, the same principles apply to molds for the casting of strands which have square or rod-like cross sections rather than the cross sections of strips. In casting these square or rod-like strands, the mold can be assembled from four separate parts which bound the four sides of the square or rodlike cross sections and which are then held in a surrounding cooling device by means of the reduced-pressure generating means of the invention.

Having thus described the invention, it is not intended that it be so limited as changes may be readily made therein without departing from the scope of the invention. Accordingly, it is intended that the foregoing Abstract of the Disclosure, and the subject matter described above and shown in the drawings be interpreted as illustrative and not in a limiting sense.

lclaim:

1. In a method of continuously casting metal in which a flow of metal is passed into and through a mold and is cooled in the mold by a cooling device surrounding the mold, the step of creating a reduced pressure between the contacting surfaces of the mold and the cooling device during passage of the metal for maintaining intimate contact between the mold and cooling device whereby uniform heat transfer from the mold to the cooling device is provided.

2. In a method as set forth in claim 1 the further step of feeding nitrogen to one end of the mold for drawing through the mold under said reduced pressure. 

